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    <title>Document</title>
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a:link{
    text-decoration: none;
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a:visited{
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a:hover{
    text-decoration: underline;
}

a:active{
    text-decoration: underline;
}
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    <h1>CSS 链接</h1>
    <p><b><a href="../css/27.html" target="_blank">这是一个链接</a></b></p>
    <p><b>注释：</b>在 CSS 定义中，a:hover 必须位于 a:link 和 a:visited 之后才能生效。</p>
    <p><b>注释：</b>在 CSS 定义中，a:active 必须位于 a:hover 之后才能生效
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